1. Field of the Invention
The present invention is generally directed to the art of trunked radio repeater systems, particularly, to a trunked radio repeater system and method providing improved communications capability for the users thereof, and, more particularly, to an improved system and method for providing a priority communication channel for use in non-emergency situations.
2. Background and Objects of the Present Invention
Systems employing repeater trunking, i.e., time-sharing of a single repeater communication channel among a multiplicity of users, are well-known, as described in applicant's U.S. Pat. Nos. 5,369,783 and 5,483,670. One of the important usages for trunked radio repeater systems is for public service trunked (PST) systems, such as the system 10 generally illustrated in FIG. 1, in which radio communications between a control site 12, containing radio repeaters, and numerous individual hand-held and other mobile radio units 14 within different metropolitan agencies are provided. As is well-known to those familiar with trunking theory, a relatively small number of such radio repeaters can efficiently service all of the needs of a public service organization within a given geographic area if they are trunked (i.e., shared on an "as-needed" basis between all potential units).
At present there are two types of trunking that may be used in the radio repeater system 10: transmission and message trunking. Typical systems, such as assignee's Enhanced Digital Access Communications System (EDACS), employ transmission trunking in group calls. Transmission trunking means that a working channel is assigned for the duration of a caller's transmission, as will be discussed in more detail hereinafter. All the other members of the called group, however, are prevented from transmitting (transmission lockout) for the duration of the message. Upon the caller's un-key, i.e., release of a Push-To-Talk (PTT) button on the aforedescribed hand-held radio 14, the system 10 immediately deallocates (tears down) the channel and makes it available for reassignment, which translates to substantially zero seconds of hang or unused time.
In message trunking systems, such as used by Motorola, however, the allocation of a particular working channel lasts longer, sometimes for at least several seconds after the user quits, i.e., stops transmitting, awaiting response from another radio. If another user responds within the predetermined period of hang time, then that working channel is used, otherwise it is released. Although message trunking may be useful in particular instances, e.g., one working channel for the duration of an emergency, message trunking is inefficient for general usage because of the necessary gaps or pauses between the users. With increased teardown and channel reallocation capabilities in current devices, particularly, using assignee's EDACS technology, it should, therefore, be apparent that transmission trunking is more efficient by eliminating hang time. Accordingly, for simplicity, the discussion hereinafter will be directed to such systems. It should, nonetheless, be understood that principles of the present invention described hereinafter, may be utilized in both transmission and message trunked systems, as is understood by those skilled in the art.
Trunked radio communications systems assign communications channels on an "as needed" basis for the exclusive use of calling mobile units requesting communications and to the group of mobile units being called. It is possible to provide much additional flexibility by pre-programming mobile units 14 in advance with several different group identifications (thus making a given mobile unit 14 a "member" of several different groups of transceivers). Since the number of groups the system can support is limited only by the RF signaling protocol providing identification of groups (and the programming capabilities of the mobile transceivers), it is possible to provide an almost arbitrarily large number of different logical groupings of transceivers as described in the aforementioned U.S. Pat. No. 5,369,783.
This trunked arrangement provides for much additional flexibility. For example, referring again to FIG. 1, a first group might be formed by all members of police squad A; a second group might consist of all members of police squad A and B; a third group might consist of a subset of police squad A (e.g., certain detectives and a supervisor); a fourth group might consist of all police supervisors from squads A and B; a fifth group might consist of all members of police squad A and all members of the rescue squad, etc.
Even though all groups are in effect "reusing" the same communications channels in this transmission trunked radio system, the trunking is mostly transparent to individual users. That is, when a police officer in police squad A switches his "channel" (actually group) selector switch to correspond to the first group and actuates his "push-to-talk" (PTT) microphone switch to make a call, his transceiver and all other active transceivers of police squad A are automatically controlled to switch to a free "working" channel temporarily dedicated to their use and no other mobile transceivers are permitted to monitor or participate in the communications over this channel.
This privacy feature afforded by trunked communications systems is important for providing each group of users with efficient, reliable communications, is critical for certain sensitive communications services (e.g., the police narcotics and detective squads) and is also critical for preventing interference from other users (e.g., the driver of a snow removal vehicle cannot interfere with communications between members of police squad A no matter what the snow truck driver does with his transceiver). Thus, in this respect the trunked system behaves from a user's view point like the prior systems in which each service had a channel dedicated to its exclusive use, while providing the radio spectrum and cost economy derived from channel and repeater sharing.
With reference now to FIG. 2, there is illustrated a more detailed depiction of the control site 12. As illustrated, individual units 14 of various groups communicate with each other via shared radio repeater channels. A dispatch console 16 may be housed directly at a repeater station site 18 or may be remotely located at other communication facilities, connected via transmission wires 20, for example, as is understood by those skilled in the art. It should also be understood that the system 10 may employ multiple dispatch consoles 16, e.g., one for each separate fleet, and a master or supervisory console for the entire system. As shown in FIGS. 1 and 2, the individual units 14 within the various groups constitute hand-held two-way radios or other such devices, for example, a radio communications system mounted within the particular vehicle, as is understood in the art.
In the aforedescribed trunked radio repeater system 10, the compartmentalization of the radio transceivers into groups is essential to effective reliable and private communications, as further discussed in the aforementioned U.S. Pat. No. 5,369,783.
Shown in FIG. 3 is an example of a currently-used communication methodology employed in one of the individual units 14 and dispatch console 16, as shown in FIGS. 1 and 2, within the trunked radio repeater system 10. For example, the aforementioned police squad A policeman's hand-held unit or walkie-talkie 14, shown in more detail in FIG. 4, remains in idle mode (box 30) when the system 10 is not in use. The unit 14 monitors the control channel for any transmissions. A transmission is indicated by a channel assignment message on the control channel instructing the group of radios to go to a specified channel to receive a call, as is well understood by those skilled in the art. If so, then the call is immediately processed (box 34) and, upon call completion, control is shifted back to idle mode (box 30). As discussed, in transmission trunked systems all of the members of the group receiving the sender's message are locked out from transmitting for the duration of the call (box 34) thereby being forced to listen.
When no call is being received (box 32), then an assessment is made whether the user of that unit 14, i.e., the policeman in squad A, is pressing his Push-To-Talk (PTT) button 14A (box 36) on his hand-held portable radio or walkie-talkie 14, as shown in FIG. 4, indicating his desire to transmit a message to the other members within that group (and/or other groups in combination therewith). If the PTT button 14A is not depressed, then control reverts back to idle mode (box 30), as described hereinbefore.
If, however, the policeman is attempting to communicate, for example, with the other policemen and policewomen within his group, then such communication is attempted (box 38) and if successful (box 40), then the transmission is sent (box 42) to the group(s) designated. If not (box 40), then control is transferred back to idle mode (box 30). As discussed, in transmission trunked radio repeater systems, when one user talks, all other users (also on the same channel) are locked out (transmission lockout) until the transmission terminates. It should, accordingly, be understood that when a group has heavy use, a waiting user within that group must compete for access with all the other group members, regardless of the criticality of the message.
It should, therefore, be further understood that in the methodology shown in FIG. 3 a given user's monopolization of the group communication pathway shuts out all the other users indefinitely. Applicant has observed that this problem has lead to group users feeling frustrated, despite a plethora of available alternate channels on the system. Further, when the talkative user finishes, all the other users must rush in en masse to get access, perpetrating the lock-out frustration. The only way another user could obtain immediate attention within the group would then be by declaring an emergency, i.e., hitting an emergency button 14B, also shown in FIG. 4, which switches all the users to a new channel for the group emergency message, as is understood in the art.
Unfortunately, there is no middle ground in current systems, i.e., no way that a user can immediately obtain the attention of a system dispatcher at the dispatch console 14 without declaring an emergency and without requiring the dispatcher to listen in on another channel, which in transmission trunked systems could be one of many possible channels. Consequently, if the aforementioned squad A policeman wishes to notify the dispatcher of an important but non-critical situation, current systems require him to fight for access with all the other users within that group or declare an emergency.
It is, accordingly, an object of the present invention to provide a system and method whereby a user can gain access to a dispatcher during transmission by another user and contemporaneously communicate with the dispatcher.
It is also an object of the present invention that the aforementioned access be rapid to avoid or ameliorate user frustrations.
It is a further object that the system and method of the present invention be compatible with existing trunk radio repeater system protocols.